A junior instructor at a San Carlos martial arts school who is accused of having sexual relations with a 13-year-old girl made an initial appearance in San Mateo County Superior Court on Wednesday, according to the district attorney’s office.Prosecutors charged 20-year-old Brendyn Crispell, of Foster City, with four felony counts of child molestation, Chief Deputy District Attorney Steve Wagstaffe said today.Crispell was arrested around 6:50 p.m. Monday after San Carlos police received reports of a suspicious vehicle in the 900 block of McCue Avenue, police said.When officers arrived, they found Crispell and the girl inside the car. Crispell allegedly admitted to a sexual act with the girl after some questioning, police said.The two met through the martial arts school and had known each other for about four years, Wagstaffe said.They had been dating for four months and, as an anniversary celebration, had allegedly decided to have oral sex, knowing intercourse was illegal but thinking oral sex was not, Wagstaffe said. He said they were in Crispell’s mother’s car and had taped blankets to the windows for privacy.Crispell is in jail, and his bail has been set at $200,000, Wagstaffe said. His next court appearance is scheduled for Wednesday.